Caspar Emilie A, Cleeremans Axel
Université Libre de Bruxelles (ULB), Centre for Research in Cognition and Neurosciences (CRCN), ULB Neurosciences Institute (UNI), Consciousness, Cognition and Computation Group (CO3).
Neurosci Conscious. 2015 Dec 31;2015(1):niv009. doi: 10.1093/nc/niv009. eCollection 2015.
In their seminal (1983) study, Libet and colleagues suggested that awareness of one's intention to act has a postdictive character in that it occurs long after cerebral activity leading to action has been initiated. Crucially, Libet further suggested that the time window (±200 ms) between the conscious experience of the intention to act and the action itself offers people the possibility of "vetoing" the unfolding action. This raises the question of whether there are individual differences in the duration of this "veto window" and which components of the readiness potential (RP) and the lateralized readiness potential (LRP) explain this variability. It has been reported that some psychiatric diseases lead to shorter intervals between conscious intentions and actions. However, it is unclear whether such patients suffer from impairment of the sense of volition, thus experiencing voluntary movements as involuntary, or whether voluntary inhibition of action is actually reduced, since conscious intention occurs later. We had two aims in the present paper. First, we aimed at clarifying the role of consciousness in voluntary actions by examining the relation between the duration of the veto window and impulsivity. Second, we sought to examine different components of the RP and LRP waveforms so as to attempt to explain observed variability in W judgments. Our results indicate (1) that impulsive people exhibit a shorter delay between their intention and the action than non-impulsive people, and (2) that this difference can hardly be attributed to a difference in time perception. Electroencephalography indicated that the rate of growth of the RP is relevant to explain differences in W judgments, since we observed that the RP at the moment of conscious intention is lower for people with late conscious intention than for people with early conscious intention. The onset and the intercept of these waveforms were less interpretable. These results bring new light on the role that consciousness plays in voluntary action.
在他们具有开创性的（1983年）研究中，利贝特及其同事提出，对自身行动意图的觉知具有事后追溯性，因为它在导致行动的大脑活动启动很久之后才出现。至关重要的是，利贝特进一步提出，行动意图的有意识体验与行动本身之间的时间窗口（±200毫秒）为人们提供了“否决”正在展开的行动的可能性。这就引发了一个问题，即这个“否决窗口”的持续时间是否存在个体差异，以及准备电位（RP）和侧化准备电位（LRP）的哪些成分能够解释这种变异性。据报道，一些精神疾病会导致有意识意图与行动之间的间隔时间缩短。然而，目前尚不清楚这些患者是意志感受损，从而将自主运动体验为非自主运动，还是由于有意识意图出现较晚，实际的行动自主抑制能力确实下降了。在本文中，我们有两个目标。首先，我们旨在通过研究否决窗口的持续时间与冲动性之间的关系，来阐明意识在自主行动中的作用。其次，我们试图研究RP和LRP波形的不同成分，以便尝试解释在W判断中观察到的变异性。我们的结果表明：（1）冲动的人在意图与行动之间表现出比非冲动的人更短的延迟；（2）这种差异很难归因于时间感知的差异。脑电图显示，RP的增长速率与解释W判断中的差异相关，因为我们观察到，有意识意图较晚的人在有意识意图时刻的RP低于有意识意图较早的人。这些波形的起始点和截距较难解释。这些结果为意识在自主行动中所起的作用带来了新的启示。
